1. Field of the Invention
The present invention relates to an observation system, and in particular, relates to technology for transmitting observation signals (data indicating observation results, such as vibrations caused by an earthquake, water pressure changes due to tsunami) acquired by submarine observation, through an optical fiber cable, for example.
2. Description of the Related Art
In a conventional submarine observation system, an observation signal can be transmitted to a land terminal apparatus from a submarine observation equipment even when an optical submarine cable is cut off. Moreover, for the purpose of enhancing utilization efficiency of the optical fiber of the optical submarine cable, the conventional submarine observation system has a structure where each of a plurality of submarine observation equipment outputs observation optical signals from two ports to two different optical fibers at the same time, and the outputted signals are respectively transmitted to two different land terminal apparatuses via different channels. (see Patent Documentation 1, for example) Furthermore, in the submarine observation system, observation equipment is laid on the deep-sea site at thousands of meters deep, and operated under harsh environment of hundreds of pressure. Therefore, if the equipment fails, immense expense is needed for its recovery and re-laying. Thus, very high reliability is required for the equipment installed in the sea.
[Patent Documentation 1] Japanese Unexamined Patent Publication No. JP2002-40152. Page 6, FIG. 1